Question: Christopher is 4 times as old as Gabriela and is also 12 years older than Gabriela. How old is Gabriela?
Solution: We can use the given information to write down two equations that describe the ages of Christopher and Gabriela. Let Christopher's current age be $c$ and Gabriela's current age be $g$ $c = 4g$ $c = g + 12$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $g$ , and both of our equations have $c$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 =$ $4g$ $-$ $ (g + 12)$ which combines the information about $g$ from both of our original equations. Solving for $g$ , we get: $3 g = 12$ $g = 4$.